Known slide fasteners (also referred to as zip fasteners) are generally constructed as follows.
A coupling portion, usually in the form of a plurality of coupling elements (also referred to as teeth) is fixed to the edge of a tape to form a stringer. The tape is usually woven or knitted and may be formed from, for example, polyester. The coupling elements may be fixed to the tape by, for example, crimping or moulding the coupling elements onto a reinforced edge of the tape. Alternatively, the coupling elements may be formed as a continuous coil having a coil-like shape formed by winding a monofilament made of synthetic resin. In this case the coupling elements are most commonly fixed to the edge of the tape while being woven or knitted into the tape or, alternatively, are stitched to a surface of the tape at the edge of the tape.
Two stringers are brought together, such that the coupling elements of each stringer can attach to one another, for example, by interdigitating, to form chain. The chain is generally planar, and the chain (and the coupling portions which form part of the chain) extends along a longitudinal axis of the chain. A slider is mounted to the chain such that it can move along the chain between the two stringers.
The slider commonly includes a main body through which the coupling elements of each stringer pass and a pull tab attached to the main body which may be grasped by a user in order to effect movement of the slider along the chain.
Movement of the slider along the chain in a first sliding direction causes the coupling elements of the first stringer to attach to the coupling elements of the second stringer. Whereas movement of the slider along the chain in a second sliding direction, opposite to the first sliding direction, causes the coupling elements of the first stringer to detach from the coupling elements of the second stringer.
The chain is cut to a desired length to form a desired length of slide fastener. End stops (often referred to as top stops and bottom stops) are attached to either end of the chain. The end stops limit the extent of movement that the slider can undertake along the chain.
Some slide fasteners, may have a single bottom stop which is attached to both the first and second stringers. Other slide fasteners, which may be referred to as a separating slide fasteners, may have two separate bottom stops respectively fixed to the first and second stringers. The two bottom stops may take the form of a retainer box and an insertion pin. The insertion pin can be inserted into the retainer box in order to attach the first and second stringers to one another. Conversely, the insertion pin can be removed from the retainer box in order to detach the first and second stringers from one another.
The invention discussed in more detail below is of most use in combination with a slide fastener of the type which has a single bottom stop.
Some slide fasteners may have two separate top stops respectively fixed to the first and second stringers. Other slide fasteners may have a single top stop attached to both of the first and second stringers.
In situations in which a slide fastener includes a single bottom stop and/or a single top stop, if significant force is applied to one of the stringers (particularly in a direction perpendicular to the sliding directions of the slider) this may cause the stringers to become detached at the bottom and/or top stop of the stringers, resulting in damage to the slide fastener and potentially resulting in the slide fastener becoming inoperable. This may occur, for example, when the slide fastener forms part of an entry opening for a dry suit via which a user puts on or takes off the dry suit. For example, when putting on the dry suit, a user may inadvertently step on one of the stringers, causing it to be urged away from the other stringer.
In order to address this problem, it is known (see, for example, Patent Document 1) to provide the slide fastener with a reinforcing strap which extends between the first and second stringers at a location proximate to the bottom stop and/or top stop as appropriate. In this situation, if significant force is applied to one of the stringers then the force is absorbed by the reinforcing strap, which prevents the stringers from being urged apart at the bottom stop and/or top stop, thereby preventing damage to the slide fastener.
Some applications of slide fastener require that the slide fastener is bent about an axis which is perpendicular to both the longitudinal axis (i.e., an axis extending in a longitudinal direction of the chain) of the chain and the perpendicular to the plane of the chain. This may happen, for example, when a slide fastener forms part of a dry suit. The slide fastener may pass over a hip and/or a shoulder of a wearer of a dry suit, this resulting in the aforementioned bending. For example, the slide fastener may pass entirely over the shoulder, even passing from the front of the drysuit onto the back. In some cases bending a slide fastener which includes a reinforcing strap whilst sliding the slider along the slide fastener may result in the reinforcing strap snagging on the slider. This in turn may result in the slider tearing the reinforcing strap and/or in the coupling elements of least one of the stringers separating from the slider rendering the slide fastener inoperable.
Furthermore, some articles which include a slide fastener with a reinforcing strap may be tight fitting, for example a dress. In such situations, whilst the article is being used, the reinforcing strap may be pushed into the coupling elements and/or slider such that, again, the reinforcing strap may snag on the slider whilst sliding the slider along the slide fastener.
Some known slide fasteners are watertight such that, in use, when the slide fastener is in a closed configuration, water is substantially prevented from passing through the slide fastener. Such slide fasteners may form part of an article which is designed to be substantially watertight, such as a dry suit. Due to the greater extent to which the coupling elements have to couple with one another within a watertight slide fastener in order to make the slide fastener watertight, it is common for watertight slide fasteners to require more force to slide the slider as compared to a standard slide fastener. The requirement for using additional force to operate a watertight slide fastener may exacerbate the problems discussed above in relation to slide fasteners including a reinforcing strap.